In a fuel cell, a cell (unit cell) 10 as shown in FIG. 7 is fabricated with plural kinds of cell components to be laminated, and a plural number of the cells 10 are laminated so as to form a stacked construction thereby securing necessary voltages. Normally, at quadrilateral peripheral edges of the cell 10, the external contour of which is rectangular, fuel gas is supplied to its anode side while oxidizing agent is supplied to its cathode side, and manifolds 10a, 10b are formed for discharging unreacted gas or produced water generated in the cell.
Here, in FIG. 8, one example of a cell construction of a polymer electrolyte fuel cell as shown in FIG. 7 is introduced. In the cell 10, a membrane electrode assembly (hereinafter referred to as “MEA”) 12 is arranged at the center of the cell 10 in its thickness direction, and on the both sides of the MEA 12, gas diffusion layers 14, 14 (gas diffusion layers 14A and 14C on an anode side and a cathode side), gas flow-path formation members 16, 16 (gas flow-path formation members 16A and 16C on an anode side and a cathode side), and separators 18, 18 (separators 18A, 18C on an anode side and a cathode side) are each arranged in this order. Moreover, MEA where the MEA 12 and the gas diffusion layer 14 are integrally formed may be called as Membrane Electrode & Gas Diffusion Layer Assembly (MEGA). Further, in the cell 10 as shown in FIG. 8 where the gas flow-path formation member 16 is formed separately from the separator 18, expanded metals or sintering madreporites are conventionally applied for the gas flow-path formation member 16 so as to function as the above-described separators (see, for example, Patent Document 1 and Patent Document 2).
In the expanded metals applied for the gas flow-path formation member 16 of the cell 10, for example, a lozenge-formed mesh 26 as shown in FIG. 9(a) or a tortoise-shell formed mesh 22 as shown in FIG. 9(c) continuously forms in a so-called zigzag arrangement. In an expanded metal 20, since the meshes 22, 26 are formed through manufacturing procedures (hereinafter explained in details) that a flat sheet material is fed to a die so as to cut the flat sheet material one layer by one layer, each of the meshes 22, 26 is fabricated connecting to each other in a stepped formation in Materials Forwarding Direction (hereinafter referred to as “FD direction” if appropriate). Generally, as shown in FIG. 9, a crossed portion of the mesh constructing the expanded metal is called as a bond portion BO, and a portion connecting between the bond portions BO is called as a strand portion ST. Further, the thickness of the strand portion ST is called as a shearing width (or feeding width) W, and the shearing width direction of the mesh is called as “WD direction.” In figures, a reference symbol t is referred to as the plate thickness of the materials while a reference symbol D is the overall thickness of the meshes 22, 26. The mesh with a long bond length BOl of the bond portion BO is the tortoise-shell formed mesh 22 while the mesh with a short bond length BOl of the bond portion BO is the lozenge-formed mesh 26. Here, since the sectional configuration of the lozenge-formed mesh 26 (A-A section) and the sectional configuration of the tortoise-shell formed mesh 22 (A′-A′ section) are identical, the sectional configuration of each of the meshes is shown in FIG. 9(b).
Furthermore, as shown in FIG. 10, since the mesh 22 (26) of the expanded metal 20 is arranged so as to incline relative to the gas diffusion layer 14 and the separator 18, triangular gas passages 24, which are diagonal-line areas in FIG. 10, are formed in a zigzag manner between the mesh 22 (26) in zigzag arrangement and the faces of both the gas diffusion layer 14 and the separator 18. Accordingly, gas flowing into the gas flow-path formation members 16 sequentially moves through the triangular gas passages 24 arranged in zigzag so as to flow in the FD direction. Here, a gas flow GF will be, as shown in FIG. 11, oscillated in a direction orthogonal to the FD direction (Transverse Direction or Tool Direction: hereinafter referred to as “Tool Feeding Direction” or “TD Direction” if appropriate) so that the gas flow GF repeats flow at very fine turns.
Still further, in order to prevent fuel gas or oxidizing agent from being leaked into the cell 10, if necessary, the MEA 12, the gas diffusion layer 14 and the gas flow-path formation member 16 are sealed with a gasket 28 typically shown in FIG. 12, nearby the manifolds 10a, 10b (see FIG. 7). The gasket 28 is made of an elastic material such as rubber, and in a condition where the expanded metals 20, each of which is composed of the MEA 12, the gas diffusion layer 14 and the gas flow-path formation member 16, are laminated, the gasket 28 is integrally formed so as to cover the external edges of the expanded metals 20.
In a sub-assembly structure in which to be sealed by the gasket 28, the MEA 12 and the gas diffusion layer 14 are not extended up to external edges at which the manifold 10a of the cell 10 is provided (the portions indicated by reference symbol S in FIG. 7), but only the expanded metal 20 concurrently functioning as a reinforcing material of the cell 10 is extended up to the external edges at which the manifold 10a of the cell 10 is provided. As shown typically in FIG. 12, the expanded metal 20 is covered by the gasket 28.
[Patent Document 1]
Japanese Patent Application Laid-open No. 2007-26812
[Patent Document 2]
Japanese Patent Application Laid-open No. 2007-188834